根据以下信息补全回函内容 You are Aakash/Varsha. You have been invited to attend the wedding of your friend's sister during summer vacation. Respond to the invitation, regretting your inability to attend it. 以下是回函不完整稿 205, Vasant Kunj New Delhi 4 March, 20XX Dear Neha Thank you for your cordial invitation on the occasion of your sister's ____1____. I, however, regret my ____2____ to be with you on this happy occasion as we shall be leaving for Shimla for summer holidays on 1 May, 20XX. Please excuse my absence. Do convey my regards and best wishes to the couple. Yours sincerely Varsha/Aakash